The brain stem and spinal cord of the lamprey, a primitive vertebrate, are relatively simple in organization, survive in isolation, contain large, visible nerve cells and axons, and exchange substances rapidly with the bathing fluid. The goal of this project to identify cranial and spinal motoneurons, interneurons, reticulospinal neurons, vestibulospinal neurons, and sensory nerve cells, to determine their interconnections by intracellular stimulation and recording; and where possible, to relate the activities of these cells to behavior, e.g., eye movements, respiration, and reflexes. A second goal is the development of the isolated lamprey brain and spinal cord as assay systems in neuropharmacology, specifically for drugs which affect identified excitatory synapses and for transmitter candidates such as glycine.